Seen a few of these and been meaning to share for a while. Was going to include in my megabed thread but figured it'd be useful as a standalone.    Dalotia or Atheta coriaria are Rove beetles. Look like storm bugs you see in the summer or miniature devil's coach horse beetles. About 4mm long as an adult and 2mm as a juvenile. They mostly live in the top 2 inches of subsoil and will eat most larval stage bugs but love thrips and fungus gnats. They are voracious and aggressive and breed